1. Field of Invention
This invention relates generally to a bearing assembly for a rotatable rudder post installed in the stern of a vessel to maintain the post at a proper position, and more particularly to a ball and socket bearing assembly adapted to align itself with a rudder post extending therethrough regardless of the degree to which the post deviates from the vertical and is subjected to hydrodynamic forces which seek to displace the post.
2. Status of The Prior Art
A sailboat, a power boat or other type of vessel is steered by a rudder in the form of a flat surfaced structure or blade hinged to the stern of the vessel and controlled by a helm. When the boat advances in a straight course, the rudder is then in line with the boat. But if the rudder is turned by the helm to one side or the other, it offers sufficient resistance to the water impinging on its surface to deflect the stern and thereby change the direction in which the boat advances.
In a typical sail or power boat installation, the rudder which is below the hull is joined to a rudder post which passes through a bronze or brass sleeve fastened to the hull, the post terminating in a lever or steering arm functioning as the helm. The metal sleeve is sealed by a packing gland affixed thereto to prevent water from entering the boat. To maintain the rudder post in its proper upright position, a bearing assembly is provided that is supported on a horizontal plate or platform cantilevered from the stern at a position below the steering arm, the rudder post passing through this assembly. The bearing assembly is adapted to sustain the side loads to which the post is subjected as well as to prevent the rudder post from slipping down into the water.
It must be borne in mind that exerted on the rudder are hydrodynamic forces whose direction depend on the orientation of the rudder relative to the water stream impinging on its surface. These forces which are transmitted to the rudder post seek to laterally displace the post. The function of the bearing assembly through which the post passes is to resist these forces which are sometimes considerable, and thereby maintain the rudder post at its proper position.
However, while a rudder post under ideal circumstances should be vertical, in a typical boat installation, the axis of the post may deviate somewhat from the vertical. Hence a conventional bearing assembly for maintaining the rudder post position, when mounted on a horizontal support in the stern of the boat to engage the rudder post, will not be in line with the post unless it is shimmed or otherwise adjusted to bring about this alignment. This complicates the installation procedure and adds substantially to the expenses involved.
A similar problem arises in propeller-driven vessels in which the rotating shaft turning the propeller may not be accurately aligned, and thereby requires a bearing assembly that will align itself with the shaft regardless of the degree to which its axis of rotation deviates from a nominal axis. Thus the patent to Waters, U.S. Pat. No. 1,067,892, shows a shaft hanger for a propeller shaft that accommodates itself to inaccuracies in alignment. The Robbins patent U.S. Pat. No. 1,063,389, and the Schmitt patent U.S. Pat. 1,025,884 also show self-aligning ball and socket bearing arrangements for motor boat propeller shafts which allow freedom of movement to the shaft in the absence of true shaft alignment.
In these prior art, self-aligning ball and socket bearing assemblies, the shaft going through the bearing rotates with respect to the bearing, whereas the bearing which is received within the spheroidal cavity which defines the socket does not itself rotate. Hence in these prior arrangements, the bearing surface is the inner surface of the bearing through which the shaft extends. Once this bearing aligns itself with the shaft, it is fixed in place within the socket which houses the bearing; hence the outer surface of the bearing which engages the wall of the socket does not act as a bearing surface.